The private-equity firm is expected to announce Monday a $2 billion equity investment in Cheniere Energy Partners LP that will allow the company to build a gas-liquefaction plant in Sabine Pass, La., according to people familiar with the matter.

Such a facility, which chills natural gas to minus-256-degrees Fahrenheit, condensing it to a shippable liquid known as liquefied natural gas, or LNG, would be the first of its kind in the continental U.S.

The investment comes as energy producers have flooded the U.S. market with cheap natural gas extracted from deeply buried shale formations, helping to push U.S. prices this winter to their lowest point in a decade. Meanwhile, global demand for the hard-to-transport fuel is rising.

In May 2011, Houston-based Cheniere won permission from U.S. regulators to export up to 2.2 billion cubic feet of natural gas per day over 20 years, potentially allowing it to capitalize on the higher prices U.S. natural gas can fetch on the global market.

U.S. natural-gas futures closed Friday at $2.55 per million British thermal units on the New York Mercantile Exchange. Global prices are pegged to oil prices and often range between $10 and $20 per million BTUs.

Some analysts have been skeptical that Cheniere could come up with the billions of dollars needed to build an export terminal. Cheniere recently reported long-term debt of nearly $2.2 billion against 2011 revenue of $269 million.

The investment was attractive to Blackstone in part because Cheniere has long-term contracts signed with four large international energy companies for capacity at the export facility, should it be built, people familiar with Blackstone's thinking said.

Blackstone's investment was made via special units in Cheniere that will convert into common units once the facility is operating, according to people familiar with the matter. It is expected to allow Cheniere to raise $3 billion in debt for the $5 billion that is needed to build the first of two planned export facilities that together will be able to ship 2.2 billion cubic feet of gas daily, these people said.

Both facilities are expected to be operating by 2016, they said.

Cheniere Energy Partners is a master limited partnership formed by Cheniere Energy Inc. that holds most of the parent company's assets. Both are publicly traded.

A prolonged slump in natural-gas prices has prompted several U.S. producers to scale back on drilling this year. Gas exports are seen as one way to bring balance back to the domestic market.

Some big users, such as Japan, rely almost entirely on imported natural gas. Less than 10 years ago, conventional wisdom had the U.S. headed toward reliance on imports as well.

At the time, several companies, including Cheniere, rushed to build gas-import terminals, which reheat the superchilled deliveries for distribution through pipelines. Cheniere built its so-called re-gas plant in Sabine Pass in 2003.

Once thought to be running out of natural gas, the U.S. is now the world's largest producer. The turnabout has reduced U.S. natural-gas imports to a trickle.